Rotor



Aug; 3, 1943.

A. LYSHOLM ETAL ROTOR 3 Sheets-Sheet l Filed Jan. 12, 1939 1N E Tom BY /1/ d ATTORNEY.

' Aug. 3, 1,943. 4 A "ILYsHOLvl dFTAL' I 2,325,617

RoToR v Filed Jan. 12, 1959 3 sheets-sheet Je@ 4f'.

ATTORNEY.

Aug# 3, 1943 A. LYsHoLM ET Ar." 2,325,617

ROTOR Filed Jan. 12, 1939 3 Sheets-Sheet 3 ENTORJ' M. ATTORNEY.

resented Agg. 3, 1943 Alf Lysholm, Stockholm, and Gustav Karl William Boestad, -'Lidingo, Sweden, assignors, by l inesne assignments, to Jarvis C. Marble, Leslie M. Merrill, and Percy H. Batten, as trustees j applicatif: :mum 12, 19:9, serai N.- 250,620 Ge rmany January 13, 1938 The present invention relates to f'ffor use in rotary compressors, and the manufacture thereof. V ,Heretofore rotors of thiskind usually have been .either die cast or `milled from a solid piece of material, and the materials heretofore used have ,usually been ordinary iron, bronze-or brass or,`in 1 ycase light rotors are desired, aluminum or like 4light-metal and the' alloys thereof.

, The procedure' heretofore followed for lforming i'orrotors of comparatively small diameter. For large rotors, die casting is not sumciently exact while the manufacture of rotors of large diameter bymilling from solid pieces of material is uneconomical because of the very expensive marequired to perform the work and also the great amount of time and waste of material inl volved in this procedure.

` rotors of this kind is satisfactory, however, onlyparts .which readily enable the rotor lobesv or teeth as well as the central portion of the `rotor to'be made hollow, thus effecting a considerable saving in weight, which is of importance not only vfrom the standpoint of weight having per se, but

also from the standpoint of the speed compressors in which the weight of the rotating masses is an important dynamic factor. The invention'is capable of being carried into eifect in many different specific ways and in order best to understand the principles of the invention and the manner in which the above stated and other and more detailed objects of the/invention are carried into eifect, reference may' be had to ensuing portion of this specification, taken lin conjunction with the accompanying drawings, descriptive of various forms of apparatus constructed in accordance with such principles.

In the accompamring drawings: Fig. 1 is a more or less diagrammaticzview,

in section, of compressor apparatus to which the present invention is applicable;

Fig. 2 is a transverse section showing the rotors ofFlg. 1;

operation of high projecting from the base 11 claims. (ciu-46s) `rotors `for rotary engines and has particular reference to v proiiled rotors with spiral 'threads orlobes Fig. 3 his' a section showing on enlarged scale v one of the rotors of Fig. 2: l

Fig. 4 is a side' elevation, partly in section, further illustrating the rotor construction;`

Fig. 5 is a partial section on enlarged scale' showing the second of the rotors oi- Fig. 2;

Figs.16 to 9, inclusive, are' fragmentary sections showing various modified forms of tooth.. construction; l

Fig. 10 is a transverse section of a rotor showing `still another formof construction; Fig. 11 is a plan View of a portion of the rotor shown in section in F18. 10; and" Fig. v12 is a transverse section-showing the form of construction of Fig. 10 applied to a' different rotor shape.

Referring n'ow more particularly to Figs.` 1 and 2, the apparatus illustrated comprises a main casing Dart i0 having' end covers I2 and il in which' are located suitable bearings for rotatably mounting the rotors It Vand Il, which are preferably geared to rotate together by means of the gears 20 and 22. l y

The apparatus illustrated is capable of being operated'either as a blower or compressor, or as a power delivering engine and since the porting required to secure the desired character lof operation is not germane to the present invention, this has not been shown. The shaft 2l extending from one ofthe rotors is utilized either as a power input or as a power output shaft depending upon how the apparatus is used. and it will be understood that if desired, in this type of apparatus, one rotor may be driven by the other and the connecting gears omitted. although the use of gearing to connect the rotors is much preferable in the type of apparatus forfwhich the present `invention is particularly vapplicable and which In accordance `with the present embodiment,

f' the tooth portions of the rotors are formed by a series of 1aminations of relatively-thin plate material. Advantageously, these laminations are stamped from such material in suitable dies .although it will be evident o course that they may be cast.

Fig. 3 illustrates the form of the laminations for the rotors It, each lamination 2l consisting of a relatively thin base ring portion 28, and a series cf peripherally spaced hollow tooth sections 3l ring. These toothsections are preferably formed as shown, with relatively thin walls, and the outer surfaces of these sectionsv are shaped to conform to thedesired tooth profile. l

These laminations are mounted on a hollow tubular shaft portion l2, and adjacent lamina- -tions are peripherally offset with respect to each other so that the several tooth sections. when assembled, provide spirally extending teeth on the rotor.

Various ways of securing the laminations to the shaft portion may be employed. In the present embodiment the tubular shaft part is provided with a dove tail slot or keyway 34 of spiral form, the pitch of which corresponds` to the pitch desired for the threads and the several laminations are formed with inwardly projecting dove tail teeth 38 shaped to fit in the slot 34. The several laminations are suitably threaded or pressed onto the shaft part axially from one end thereof to form the rotor assembly.

It will be evident that these laminations may be suitably keyed in other ways as, for example, by welding onto the lsurface of the shaft part 32 a spiral key and providing laminations with suitable keyway recesses enabling them tobe threaded over the key.

A rotor thus formed may be mounted in any suitable manner, by means of bearings mounted within the hollow shaft part or, as in the embodiment illustrated, by means of the end parts 38 (Fig. 4) inserted in and suitably secured to the central .shaft part or sleeve 32. The laminations may be retained in place in any suitable desired manner as by welding or brazing them together, or by making them a tight press t on the central sleeve. If desired, the rotor structure may be strengthened by forming certain of the laminations withsolid rather than hollow tooth webs. as indicated at I in Fig. 4.

It will be understood that when the rotor is assembled in this manner, the flanks of the teeth will present a series of steps rather than the smooth surface which is desired for the finally finished rotor. The machiningrequired, however, to form the finished surface from these stepped surfaces, which are, to begin with, shaped -to the desired profile and pitch, requires relaltively little work and the removal of very` little material. It will further be evident that the amount of machining (that is, cutting, grinding, or the like), required to bring the rotor teeth to final form, will depend on the thickness o-f the plates used. If plates of very thin material are used. the amount of finishing 'required-may be reducedto very little. v

Fig. illustrates the construction employed in making the rotor which cooperates with the rotor shown in Fig. 4. In this construction a hollow sleeve 42 is provided which forms the central shaft portion of the rotor and upon which a series of peripherally offset laminations 44 are assembled. These laminations, as in the rotor previously described, are formed with a base ring pore tion 46 and a series of projecting teeth or lobes 48 shaped to provide intermeshing cooperation between the teeth and spaces of the two rotors. Because of the form of the teeth of this rotor, they may advantageously, when made of hollow form, be reinforced by means of circumferentially extending webs 48a.

The plates Il in this instance are also provided with inwardly projecting teeth 50 adapted to be received in a spiral slot 52 in the sleeve I2.

The manner of assembling this rotor will be evident from the description oi the rotor shown in Figs. 3 and l4.

In the embodiment Just described, the rotor arrangement employs a male rotor |16 having four 5. teeth, cooperating with a female rotor having lsix. It will be evident, however, that in so far as the present invention is concerned, the number of teeth `employed and the combination of the numbers of teeth of cooperating rotors is immaterial, these factors as well as the factor of the specific tooth profile not affecting the principles of rotor construction contemplated by the invention.

In a further embodiment of the invention, the rotor teeth are built up of a series of laminations, each for a single tooth, and the several laminations being secured directly to a central shaft sleeve.

Referring now to Fig. 6, this form of construction is illustrated, comprising a central shaft sleeve 54 provided with a series of spirally directed dove tail slots 56, 58, and 60. A series of plate sections or laminations 82 areprovided, each corresponding in profile to the desired tooth stion and having side walls 62a. and 62h terminating respectively in feet 82e and 624i shaped to fit in y the slots. Central radial reinforcing webs 52e may also advantageously be provided, these webs having feet 82j adapted to be received in the slot 58. It is believed that the manner of construction of the tooth will be evident from the above description and, all of the teeth being of like construction, it is suicient to describe but one.

Fig. 7 illustrates a modification of the general form of construction shown in Fig. 6, the tooth sections 64 being provided with side walls 64a and 84h each having feet adapted 'to be received respectively in suitable spiral slots in the central sleeve. In this form the stiiening of the tooth sections is provided by means of a transverse web Btc which enables one of the dove tail slots to be eliminated.

Fig. 8 shows still another embodiment in which the sections 86 are provided with crossed reinforcing webs 68 and l0. In this embodiment the web 68 is provided with a dove tail foot 68a, received in a corresponding dove tail spiral slot 1li in the central sleeve. This dove tail foot serves to retain the lamination against radial displacement and the side walls 66a and 66h are in this instance provided with feet which are received in open grooves or slots 'l2 and 14 of spiral form.

Still another form of tooth section is shownin Fig. 9 in which the side walls of the laminations Y 16 are received in open spiral slots 18 and 80 in the sleeve and the sections are retained against radial displacement by means of dove tail feet 82 and 84 formed at the inner ends of radially extending reinforcing webs 16a and 1Gb, and retained in suitable dove tail slots in the spiral sleeve. From the above it will be evident that in accordance with the principles of the invention the tooth laminations may be formed spirallyof substantially any desired specific section and separately assembled, and it will be apparent that for manufacturing reasons the dove tailing i nay be limited to only a part of the groove strucure.

Figs. l0 to 12 illustrate another form of con, struction particularly suited for making rotors of simple cast sections suitable for productipn by die casting methods. In this form o1 construction a series of cast sections 86 are provided, each having an axial length X and provided on their axially opposite ends with dove asador? tail slots and projections Il and Il respectively. These sections. which constitute relatively thick laminations. are formed with the sides of the teeth corresponding substantiallyto the desired iinished surfaces of the teeth and are assembled in circumferentially onset relation onl a central hollow shalt sleeve I2. The extent oi the circumierential onset o! the sections relative to each other is determined by suitable location of the slots and projections which. as will be observed from. Fig. 10, are formed so that the sections may be assembled by movement of the several f sections laterally with respect to eachother into engaging relation. Ai'ter the sections are assembled in this mannenthe central sleeve is inserted. this member acting as a locking member preventing lateral displacement of the several sections relative to each other in the direction oi the slots.

In rotary apparatus of the kind embodying lntermeshing screw threaded rotors operating at 4high peripheral speeds. clearance between the operating conditions. Heat of compression' will tend to make rotors o! the kind under consideration expand and in order to avoid adversely ailecting the eliiciency oi operation of the apparatus it is desirable to use materials having low or negligible coemcients of expansion. Qne very suitable material having substantially negligible expansion coemcient is the variety of nickel-iron alloy in which the nickel content is oi' the order of from 32% to 40% and the iron content is oi' the order of from 68% to 60%. This material is commonly known as Invar." This material and other special materials are. however, relatively expensive as compared with the ordinary metals and the-present invention is particularly advantageous in connection with the use of such special materials since the amount of'material required to be used is relatively little as compared with that required for conventional forms ot rotor construction.

From the foregoing vit will be apparent that th invention may be embodied in numerous different speciilc forms of apparatus and the invention is accordingly not to be considered as restricted tothe forms shown herein by way of example but is to be understood as embracing all rotor forms falling within the scope of the appended claims.

What is claimed is:

1. A rotor for compressors and the like comprising a hollow body portion of generally cylindrical form having a peripherally continuous wall and a plurality of hollow helicaltooth' portions carried by said body portion, said tooth portions being formed by a plurality of sections oi like profile arranged in axially abutting relation and peripherally displaced with respect to each other to provide continuous tooth portions of helical form.

2. A rotor i'or compressors and the like comprising a.hollow body portion of generally cylindrical form having a peripherally continuous wall and a plurality of hollow helical tooth portions carried by said body portion, said tooth portions being formed by a plurality of thin laminations oi like profile arranged in axially abutting relation. and peripherally displaced with respect to '5 drical iorm having a 'peripherally continuous wall and a plurality of helical tooth portions carried -by said body portion, said tooth portions being formed by n.- plurality oi' thin laminations oi' like pronle arranged in axially abutting relation and peripherally displaced with respect to each other to provide continuous tooth portions o! helical form, the maior portion of said laminations providing hollow tooth sections and certain ot said laminations providing solid tooth sections, the laminations having the solid tooth sections being spaced axially from each other along the length orthe rotor to stillen the several teeth oi? the ro r. v

4. A rotor for compressors and the like comprising a hollow body portion of generally cylindrical form having a peripherally continuous wall and a plurality of hollow helical tooth portions carried by said body portion, said tooth portions being formed by a plurality of sections of like profile arranged in axially abutting relation and peripherally displaced with respectto each other. to provide continuous tooth portions of helical form, each of said sections having a plurality of hollow tooth pronle portions peripherally spaced 3o upon and connected by a peripherally continuous base ring portion ilxed to said body portion.`

n 5. A rotor for compressors and the like comprising a hollow body portion of generally cylindrical form having a peripherally continuous wall and a plurality of hollow helical tooth portions carried by said body portion, said tooth portions being formed by a plurality of thin laminations of like proille arranged in axially abutting relation and peripherally displaced with respect to each other to provide continuous tooth portions of helical form. each ci' said thin laminations having a plurality of hollow tooth proille portions peripherallyy spaced upon and connected by a peripherally continuous base ring portion. ilxed to said body portion. i 6. A rotor for compressors and the like comprising a hollow body portion oi generally cylindrical form having a peripherally continuous wall and a plurality of hollow helical tooth portions carried by said body portion, said tooth prtions being formed by a plurality oi' sections oi' like profile arranged in axially abutting relation and peripherally displaced with respect to each other to provide continuous tooth portions of helical form, each o1' said sections having a. plurality of hollow tooth proille portions peripherally spaced upon and connected by a peripherally continuous base ring portion xed to said body portion, the end walls oi adjacent sections being provided with mutually interengaging transversely extending grooves and projections for locating the several sections peripherally with respect to each other, said projections and grooves permitting assembly and disassembly o! the sections laterally of each other in the absence of said body portion -and said body portion acting topi-event lateral displacement o! the sections relative when the rotor is assembled.

7. A rotor for compressors and the like com.

and a plurality roi' hollow helical tooth portions carried by said body Portion. each of said tooth portions being formed by a plurality of axially adiacentapertured sections peripherally disto each other asador! pricing a hollow body portion of generally cyline drical form having a peripheraliy continuous wall and a pluralityo! hollow .helical tooth. portions carried by said body portion, each of said tooth portions being formed by aplurality oi' axially adjacent apertured sections having said walls formed to substantially coincide with the desired walls formed to substantially coincide with the v desired proille, said side walls-being of substantially uniform thickness and fixed respectively directly to the wall of said bodyportion to provide I y continuous tooth portions of helical form.

9. A rotor for compressors and the like comprising a hollow body portion of generally cylindrical form having a peripherally continuous wall and a plurality of hollow helical tooth portions carried by said body portion, each ot said tooth portions being formed -by a plurality of,

axially adjacent apertured thin laminatioms havproille, said side walls being of substantially uniform thickness and being connected by a trans 'versely extending stiiltening web, the base of each oi said side walls being fixed directly to said body portion to provide continuous tooth portions of helical form.`

11. A rotor for compressors and the like comprising a hollow body portion consistingof a o cylindrical tubular member having a plurality of spiral grooves formed on its exterior surface `and a plurality oi helical teeth formed on said member, each o1' said teeth consisting of a pluing sidewalls formed to substantially coincide with the desired prole, said side walls being of substantially uniform thickness and iixed respectively directly to the wall of said body portion f to provide continuous tooth portions ot helical form. il

10. A rotor for compressors and the like comrality o! relatively thin laminations having rela-g tively thin side walls curved to substantially desired tooth prole, the base portions' oi said side walls being located in said spiral grooves and 'ilxed to said body member, whereby to form a plurality of substantially hollow helical teeth on said body member.

lam LYsHoLM.

GUs'rAv t1-i. i y

` 7 BOESTAD. 

